Yes, I know that picture here is the best explanation. But it is so annoying to make pictures. Especially here, since it should be some kind of gif. So if someone who understands this place draw a picture and put it to the editorial it will be awesome 
What I don’t understand is that how would we able to move the vertical circles to a somewhat diagonal position thereby increasing D(for the optimum fit) if the circles X=W/2 ie the circles are perfectly fit
Thanks a lot for your help!I was missing the vertical gap(the wasted steel) which instead of taking in the centre(b/w circles and lateral surface) I had taken on the right side of the lateral surface.